This invention relates to an improved construction for a reinforced door structure.
Thermosetting resins have found increasing use not only as surface compositions for desk and counter tops, but also as decorative profile extrusions for replacement of prefinished wood moldings. Products such as window frames, wall panelling, stair rails, siding and doors are now fabricated from plastic and are commercially available. The use of plastic in such applications has been attributed to factors such as shortage of available wood, and the high cost of skilled labor, both of which have contributed to the increase in cost of finished wood products. However, plastic products have certain inherent properties which have stimulated their use as a replacement for wood products. For example, plastics have superior properties such as resistance to denting and marring, resistance to fungi and pest attacks, and resistance to shrinkage and swelling produced by variations in temperature and humidity. In addition, quality control is relatively easy to maintain to insure proper construction to give superior thermal and acoustical insulating properties, along with structural integrity.
These factors have encouraged design engineers and manufacturers to investigate the suitability of various plastics to a wide range of building products. Commercially available plastic doors meet many of the abovementioned criteria; however, dimensional stability, which can be described as resistance to shrinkage and swelling, that is, to deformation under the action of humidity, cold and heat, has been less than satisfactory. This unsatisfactory performance has been especially noticeable when the exterior side of a plastic door is exposed to conditions of high humidity or low temperature, while the interior side is maintained at a comfortable ambient. Warping and bowing of the door can occur, leading to difficulty in opening and closing of the door, and possible structural damage.